I've dealt as both buyer & seller on ebay since almost its inception.

Ebay was, earlier on, a lot like Gumtree is now, in so much as it was a great place to sell off unwanted items around the house, & buy at a very competitive price when you wanted a particular item.

As time went on ebay became a venue for people who wished to run a high volume sales set-up from home. This in turn was upsetting to big business (Hardly Normal & their ilk), as ebay sellers were not burdened by having to allow for overheads on the final sale such as paying staff, warehouse rental etc. So some of these firms began selling on ebay also, however, ebay was still a great place to get a good price. 

I've found in recent months that if I research a particular item on ebay, get the best price available, then go to the store, haggle, and offer cash settlement, that the price will be better than available on ebay. Having to attend the store is no more a hassle than having to attend the post office. Perhaps this has a bearing on why some sellers are complaining about fewer sales nowadays.

Some of ebay's policies don't help either.

Just my thoughts on this matter.